The present invention relates to the field of stereoscopes. In particular, the present invention relates to a prism stereoscope for viewing stereoscopic image pairs.
Stereoscope viewing apparatuses have been known since 1833 when Sir Charles Wheatstone, a British inventor, came up with the idea of using drawings and a viewing device to produce three dimensional images. The drawings included two side-by-side complementary images, each image drawn from a slightly different perspective. When placed a fixed distance from a users eyes, and with the help of a septum, the images fuse together to produce a three dimensional effect.
As the stereoscope technology advanced, side-by-side complementary photographs took the place of the drawings. Over the years, many types of stereoscopes have been used. The following patents describe such examples:
The side-by-side format is a popular method of displaying stereo-paired images. Commercial stereoscopes, such as the Holmes/Bates and Viewmaster(copyright) stereoscopes typically contain lenses combined with prisms. Lenses magnify the images and allow the user to focus on the images a few inches from the user""s eyes. The prisms also translate the images to the center of the user""s field of view. This aids the user in fusing the images in binocular vision.
Many commercial stereoscopes incorporate prisms intrinsically as a property of the lens. Lenses in stereoscopes define a limited range of viewing distances for which the user can focus on stereoscopic images. The limited range, together with the amount of prism action, define the maximum separation of the images that can be fused. Therefore, either the stereoscope determines the allowable image separations or the image separation determines the required properties of the stereoscope.
The use of standard image sizes became popular early on in order to allow standard stereoscopes to be used to view many images. However, images are increasingly being printed or viewed in non standard sizes. Non-standard sized images are frequently encountered when a computer monitor is used to view the stereo-images. This is because the size of the images depends on the properties of the monitor, including monitor settings such as pixel density, and the pixel dimensions of the images. Stereoscopes often use a septum to block out the periphery around the images including the well-known side images which cause visual rivalry between the left and the right views. The optimal dimensions of the septa are determined by the distance between the stereoscope and the stereo-image pairs and the properties of the lenses. In traditional stereoscopes, the septum has a fixed geometry.
To aid the viewing of non-standard size images, various stereoscopes have been designed using prisms or mirror boxes. Mirror boxes typically allow large images of a particular size to be viewed at any distance. If the mirror box can be translated outward, a range of large image sizes can be used at any reasonable distance. However, mirror box stereoscopes are typically as wide as the distance between the centers of the images being viewed.
Stereoscopes which use prisms but no lenses can be used to view images of any size from the common standard print sizes up to arbitrarily large sizes. The user adjusts the viewing distance until the stereo images fuse together. Prism stereoscopes often include masks to block out the well known side images which create vision disparities between the left and right eyes. Ideally, the masks should block out all of the periphery from the fused image.
The present invention is a stereoscopic viewing apparatus for viewing side-by-side complimentary pairs of stereo images. The stereoscopic viewing apparatus of the present invention includes a pair of ocular members and a pair of objective members. In use, the ocular members are placed proximate to a user""s eyes, and the objective members are adjusted to define a field of view. The objective members are adjusted depending upon the size of the stereo images and the distance the stereo images are from the viewing apparatus. With the objective members properly adjusted, the user perceives a three-dimensional image.